1. Field of the Invention
The present invention relates to a piezoelectric resonator and an electrode structure thereof, and more particularly, to an electrode structure of a piezoelectric resonator having high reliability and low manufacturing costs, and a piezoelectric resonator including the same.
2. Description of the Related Art
A piezoelectric resonator generally has several uses such as a frequency oscillator, a frequency regulator, a frequency converter, or the like. Quartz having excellent piezoelectric characteristics is used as a piezoelectric material in a piezoelectric resonator. This quartz serves as a stable mechanical vibration generator.
In this case, quartz used as a piezoelectric material is artificially grown in a high pressure autoclave and is cut based on the axis of a crystal, and the size and shape thereof are processed so as to have desired characteristics, such that the quartz has a wafer shape. Here, the quartz is required to have a low phase noise, a high quality (Q) value, and a low frequency change rate for a change in time and environment.
Here, the Q value indicates band selection characteristics in a resonator, a filter, an oscillator, or the like, and is called a quality factor. In addition, the Q value may be determined to be a ratio of a central frequency to a 3 decibel (dB) bandwidth. The larger the Q value is, the better the frequency selection characteristics of the oscillator are.
As an electrode structure for a piezoelectric resonator according to the related art, a two-layer type of electrode has been used.
In the case in which a change in an external thermal environment, such as during a soldering process when a piezoelectric resonator is manufactured, is generated, an oscillating frequency of the piezoelectric resonator is varied. The varied frequency returns to an original frequency over time.
The frequency variation characteristics according to the change in thermal environment have caused an increase in product lead time and a limitation in using a product requiring frequency deviation accuracy of the piezoelectric resonator.
Therefore, various attempts have been made in order to improve the frequency variation characteristics of quartz.